My doctor told me that I have got a deficiency of Vitamin D. He had asked me to include a lot of fish and dairy products in my diet.
I have been suffering from periodontal disease. I suspect this lack of Vitamin D as the main reason behind my periodontal disease. I am planning to consult a general dentist ( http://www.skyviewdental.ca/meet-our-team/our-team/ ) in Aurora next month in order to find a solution to this problem.
Is periodontal disease linked to Vitamin D deficiency? Apart from fish and dairy products, which all food items should I include in my diet in order to increase the Vitamin D?

Yes, periodontal disease is linked to Vitamin D deficiency.
Here is the problem. Your doctor is asking you to solve your deficiency through “food” and I guarantee you will not be able to do this. The only way is thru sunshine or supplements. There is not enough in food to keep a human healthy.
Now to get enough if any from sunshine you would need to read the section on https://www.vitamindcouncil.org/about-vitamin-d/how-do-i-get-the-vitamin-d-my-body-needs/. Most people do not live at a latitude that is conducive to Vitamin D production all year and therefore need to take a supplement or get a sunlamp to use for fall and winter. (This means Ontario.)
As for supplements we recommend the following. We believe in maintaining a “healthy” minimum Vitamin D level of 50ng/ml (125nmol/l). This is because at levels below 40ng/ml (100nmol/l) science has proved that your chances for cancer or autoimmune disease increases “dramatically”.
This means the average weight person of 150lbs needs to take 5000 iu of Vitamin D3 a day. (If you weigh more, you have to take more.) If you are extremely deficient, then most doctors treat with the equivalency of 7-8000 iu a day for 8 weeks and then retest to make sure you have reached an adequate level.